Your water heater is leaking
Where the water is coming from decides whether this is a repair or a replacement.
Is this an emergency?
You’re probably seeing
- A puddle underneath or around the base of the tank
- Water running from the discharge pipe near the floor
- Dampness or rust staining on the top of the tank around the inlet and outlet
- A steady drip from the drain valve at the bottom
- Rust-coloured water at the taps, or a rumbling noise from the tank
What it probably is
A loose or corroded inlet or outlet fitting
Common - and the most straightforward repairThe water is on top of the tank or running down the side from a connection at the top. The tank base is dry.
A leaking or partly open drain valve
Common, and often an inexpensive partA drip from the tap-like fitting at the bottom front of the tank, often after someone has drained or flushed it.
The temperature and pressure relief valve discharging
Common - and the one people misreadWater from the pipe that runs down the side of the tank towards the floor. This may be the valve failing, or the valve doing its job.
Condensation rather than a leak
Worth ruling out before paying for a call-outA small amount of water on a cold morning, on a gas heater, that does not return once the tank is up to temperature. Most common on a new or recently refilled tank.
The tank itself has corroded through
Common on older tanks - and it is a replacementWater emerging from the bottom of the tank with dry fittings above, often with rusty water at the taps. Usually on a heater past about ten years.
Excess pressure in the system
Less common - but it is a system fault, not a heater faultThe relief valve discharges repeatedly, and you may hear banging in the pipes. A failed expansion tank or a high incoming pressure.
What to do before anyone arrives
Turn off the power or the gas to the heater
On an electric heater, switch off its breaker. On a gas heater, turn the gas control dial to OFF or PILOT. A tank that loses water while still heating can be damaged, and an electric element that runs dry fails quickly.
If you smell gas at any point, stop, leave the house and call the gas utility from outside. Do not switch anything on or off.
Shut off the cold water supply to the tank
There is a valve on the cold inlet pipe entering the top of the heater. Turning it off stops the tank refilling as it empties. If you cannot find it or it will not move, use the main shut-off for the house.
Work out where the water is actually coming from
Dry everything thoroughly, put paper towel under the likely points, and look again in twenty minutes. Top of the tank means a fitting. The pipe running down the side means the relief valve. The bottom front tap means the drain valve. Straight from the base with dry fittings above means the tank.
If it is the relief valve, do not touch the valve itself
The temperature and pressure relief valve exists to stop the tank becoming a pressure vessel. It discharges when temperature or pressure is too high, so a valve that keeps releasing water may be reporting a genuine fault elsewhere.
Never cap, plug or block the discharge pipe, and never tighten a relief valve to stop a drip. This is the one part of a water heater where the failure mode is a rupture.
Get the water up and start drying
The EPA advises that wet buildings and furnishings must be dried within 24 to 48 hours in order to avoid mould growth. On a heater in a finished basement or a closet, this matters as much as the repair.
Note the age of the heater before you call
The manufacture date is on the rating plate, often encoded in the serial number. It decides the conversation: on a tank past about ten years with a leak from the base, the honest answer is replacement, and knowing that in advance protects you from paying to be told it.
This is the end of the homeowner sequence. Do not attempt to replace a relief valve, an element or a thermostat on a live tank.
What it costs to fix
Ranges below are for the repair itself. For full replacement pricing see the plumbing cost guides.
| Where the leak is | Is it repairable? | What decides your bill |
|---|---|---|
| A fitting at the top of the tank | Usually yes | A short labour job, plus access around the tank |
| The drain valve at the bottom | Usually yes | An inexpensive part and a short visit |
| The T&P relief valve or its pipe | Yes - but find out WHY it discharged | Whether it is the valve or a pressure problem in the system |
| Condensation, not a leak | Nothing to repair | Nothing, if you confirm it before calling |
| The base of the tank itself | No - the tank has corroded | This is a replacement quote, not a repair quote |
U.S. Bureau of Labor Statistics, Occupational Outlook Handbook (May 2025 wage data).
We do not print a national installed price for a water heater replacement, because tank versus tankless, fuel type, venting and local labour move it more than any average can carry, and the aggregator figures that publish one are undated. What you can anchor on: the national median wage for plumbers, pipefitters and steamfitters is $30.67 an hour (BLS, May 2025), billed on top of a call-out. The single most useful thing you can do before quoting is establish where the leak originates - it determines whether you are buying an hour of labour or a new appliance.
Can I fix this myself?
A water heater holds scalding water under pressure. CPSC records that a five-minute exposure to 120°F water can cause third-degree burns, and that most adults suffer third-degree burns from two seconds at 150°F. Do not raise the thermostat while troubleshooting, and let a tank cool before draining it. Never cap or block a temperature and pressure relief discharge pipe.
Reasonable to DIY
- Switching off the breaker or turning the gas control to OFF
- Closing the cold water inlet valve
- Drying the area and getting standing water up
- Locating the source of the leak with paper towel
- Reading the manufacture date off the rating plate
Call a pro
- Replacing a temperature and pressure relief valve
- Replacing a drain valve on a full or hot tank
- Any element, thermostat or gas control work
- Diagnosing why a relief valve keeps discharging
- Replacing the heater, and the venting and expansion tank that go with it
Making it safe is genuinely yours: power or gas off, water off, dry the floor, find the source. That takes fifteen minutes and it is the part that limits the damage. The repair is not yours, and on a tank leaking from its base there is no repair to attempt - the useful thing you can do is arrive at the conversation already knowing the age of the unit and where the water is coming from.
Is this covered by insurance?
Whether a claim is worth filing depends on the cause, your deductible and how the damage happened - not on the repair price alone.
Sources
Sources last checked
- Tap Water Scalds (CPSC Publication 5098)U.S. Consumer Product Safety CommissionRetrieved 2026-09-14
- Plumbers, Pipefitters, and Steamfitters - median pay, May 2025U.S. Bureau of Labor Statistics, Occupational Outlook HandbookRetrieved 2026-09-14
- Mold Course Chapter 2: Why and Where Mold GrowsU.S. Environmental Protection AgencyRetrieved 2026-09-14
Sources for the figures and the legal requirements cited on this page.
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